Electronic devices may perform operations involving critical information such as personally identifying information, account information, medical information, business information, or various other types of sensitive information that has economic or other value. Such devices may be ripe targets for hackers or other attackers who seek to access such critical information through eavesdropping or hacking devices. For example, an attacker may attempt monitor signals that are transmitted to or received by devices, as well as signals that are internal to the devices. This may be done by non-invasive or invasive means. In many cases, attackers attempt to physically access components of the device, such as one or more communication lines carrying data or a processor that communicates and processes payment information. Attackers may also attempt to simulate an external device or internal components of the device under attack. Accordingly, device makers employ a variety of methods to encrypt and protect critical information, safely store cryptographic information, and to identify and prevent tamper attempts.